Power supply cover with fused outlets

thingiverse

This is the 3rd version of a project that started about four years ago and was followed by an improved version a few months later. I have used these power supply covers with all my 3D printers and laser engravers in the past years without seeing any need for improvements until one day when I created a short in one of the attached power cables. As these cables were only used on a device that uses less than two amps, they were dimensioned accordingly so the short did not burn the fuse of the powerful 30 amp PSU but rather caused the relatively thin cable to start burning within seconds. That's when I realized how dangerous a powerful PSU can be if used without a fuse that is dimensioned according to the actual intended use. The built-in fuse or over-current protection which traps only when the maximum amperage of the power supply is exceeded will not prevent damage to attached circuits which only use a fraction of the maximum possible amperage. So this is why I went back to look at the design of my power supply cover again, this time with the aim of protecting each power outlet with its own fuse whose value can then be chosen to fit the current used by the attached circuits. In this version of the project, I added an automotive fuse holder for each of the three power outlets. These fuse holders use standard medium size blade fuses and can be ordered cheaply from eBay or AliExpress. I paid USD 1.06 per lot of five. These fuse holders come also with a plastic cover which we don't use here to save space. Instead of wiring the twelve volt output directly to the Molex or Tamiya sockets, the PSU twelve volt output now goes first through the fuse and only then into the socket. This allows us to protect each twelve volt output with a fuse that is specific to the intended use of the outlet. In my unit here, I have protected the three outlets with fifteen amp, ten amp, and five amp fuses respectively. Thus, the heatbed will be connected to the fifteen amp outlet at the left and the extruder and motors to the ten amp outlet in the middle. The five amp outlet at the right is a spare output that can be used to attach other gadgets. Another enhancement made in this version is to provide a choice of AC power switches. In addition to the small ten millimeter by fifteen millimeter rocker switch used in the previous version, the bigger fifteen millimeter by twenty-one millimeter switch is now also supported. For all the rest, this version is identical to the previous version so please refer to there for further information on this project. In the files section, you will find the fully parameterized OpenScad source together with ready-to-print STL files for Molex 19-09-2029 and Tamiya connectors in versions with and without fuse holder and for ten by fifteen millimeter and fifteen by twenty-one millimeter AC rocker switches. Note that for the Molex versions you also need to print the corresponding clips, and for Tamiya versions the corresponding frame object is needed. Note that I myself only use the Molex version of this project while I also try to keep the Tamiya versions updated I have not actually built them so I cannot guarantee that they will work perfectly. Update 2018-12-17: There is now a smaller more compact version of the twelve volt thirty amp power supply on the market so I have published today a new version of this project adapted to the new small form factor device.